This invention relates to a production method of a thin film magnetic head for use in a magnetic drum, magnetic tape or magnetic disc of a magnetic recording equipment.
The thin film magnetic head is a magnetic head which is produced by thin film technique in order to enhance the magnetic recording density of the magnetic drum, magnetic tape or magnetic disc. Generally, the head has a laminate structure in which lower and upper magnetic films for forming a magnetic circuit having a magnetic gap and coil conductor films passing between both magnetic films and crossing the magnetic circuit are laminated at necessary portions of a substrate via an insulating member. At times, a part or the entire portion of the substrate is made of a magnetic substance and serves as the lower magnetic film depending upon the intended application.
The major problems with the thin film magnetic head that are yet to be solved are (1) reduction of the size of the device and improvement of magnetic characteristics such as reduction of writing power and improvement of reading sensitivity and (2) provision of a high precision structure which is easy to produce.
As one of the methods of solving these problems, a method is known in which a photosensitive resin is used as the insulating member between the lower and upper magnetic films. This method is described on page 4 of "IBM Disk Storage Technology", February, 1980, for example. According to this method, the recesses (gaps) defined between the windings of the coil conductor films are filled with the resin so that the upper surface of the insulating member at the winding portions of the coil conductor films are flattened and hence, the surface of the upper magnetic film to be formed thereon is also flattened. As a result, permeability can be drastically improved when compared with the surface having concavo-convexities thereon. In accordance with this method, too, the pattern accuracy of the insulating member can be improved in comparison with the case in which an insulating member other than the photosensitive resin is to be etched, because the etching mask is not necessary.
In spite of these advantages, the insulating member consisting of the photosensitive resin is not free from the drawback in that since its heat resistance is low, the upper magnetic film to be formed thereon must be formed by such a method that hardly involves the temperature rise. The following problems would occur if such a method is used in order to form the magnetic film.
Plating can be cited as one of the methods that hardly involve the temperature rise. However, the film composition is caused to drastically change even by a slight change of the condition and consequently, the film having desired magnetic characteristics can not be obtained easily with good reproducibility. In addition, control of the film thickness distribution is difficult and a uniform film thickness can not be obtained. Moreover, an apparatus for treating the waste liquor is necessary.
Another method of forming the film that does not involve the temperature rise is vacuum evaporation or sputtering. However, when a several micron-thick film necessary as the upper magnetic film is formed by these methods while keeping the substrate at such a temperature that does not adversely affect the insulating member, the resulting magnetic film has perpendicular magnetic anisotropy having the easy axis of magnetization in the direction of film thickness because of the internal stress and the permeability becomes as low as up to 300. If the thin film magnetic head is formed by use of the magnetic film having such low permeability, the drop of reading sensitivity and recording density would occur and the advantages of the thin film magnetic film can not be used fully.